Persistent infection of mink with Aleutian mink disease parvovirus (ADV) leads to progressive immune disorder characterized by high levels of antiviral antibodies, hypergammaglobulinemia, plasmacytosis, and immune complex disease. Virus is not neutralized in vivo and ADV exists in infectious immune complexes. Isolates of ADV differ markedly in their ability to induce AD; some like ADV-Utah and ADV-TR are highly pathogenic in vivo, but are replication defective for CRFK cells. The cell-culture ADV-G is replication competent for CRFK, but replicates poorly, if at all, in mink and does not cause progressive disease. A major goal of this project is to correlate specific DNA sequences of the ADV genome to functional correlates, such as pathogenicity determinants and strain variation. Another major goal is to study the actual structure of the ADV virion. Understanding of the structure at high resolution will enable us to (a) map epitopes and pathogenicity determinants to discreet coordinates on the viral particle, (b) define sequences necessary for virus assembly. A summary of the results obtained within the last year includes: * Structural studies of ADV. Using cryo-electron microscopy of virions expressed by recombinant baculoviruses, the structure of ADV has been resolved to 22 Angstroms. The surface of the virion has several unique features not observed in other parvoviruses. Crystallization studies have been initiated. Full-length capsid proteins have also been expressed in E. coli and Pichia pastoris and purified to near homogeneity. Methods to drive self-assembly of these proteins into particles are being developed. * Analysis of chimeric virus constructions. Additional full length clones chimeric between ADV-G and ADV-Utah have been analyzed. Complex determinants for in vitro replication competence map to sequences within the capsid proteins. Detailed mapping indicates that non-contiguous sequences interact or "cross-talk" to form these determinants. Two chimeras, replication competent for CRFK, were found to induce viremia and anti-ADV antibody in adult mink.